Understanding and using Pie Charts
How do I read a Pie Chart?
To read a pie chart, you must consider the area, arc length, and angle of every slice. Because it can be hard to compare the slices, meaningful organization is key. Slices in a pie chart should be organized in a coherent way, usually the biggest to smallest, to make it easier for the user to interpret. Start at the biggest piece and work your way down to the smallest to properly digest the data. The colors of the slices should match their respective blocks in the legend, so that viewers do not need to consult the legend as much.
Generally, the whole (or total of the quantitative values or slices) is not listed within the pie chart. Typically, it can be listed in the text near the chart, the table explaining specific data measurements, or as a separate BAN in another dashboard.
Three-dimensional pie charts are difficult to read and misleading. Since the interpretation of a pie chart relies on the area, arc length, and angle of each slice, a three-dimensional representation of this chart type will tilt the pie and skew your visual perception of its slices.The use of a three-dimensional pie chart can make an accurate comparison of categories nearly impossible due to the visual imbalance that can exist between slices.
This pie chart takes data from the east market sales and splits them by the variety of coffee purchased.
- This chart shows two radically different data points easily distinguished from each other
- The dominant slice has a bold color
- The smaller slice has a neutral/subdued color
Further considerations and supplemental material
Bar charts and stacked bar charts can be good potential alternatives to pie charts. They can better show the relative size and importance of measure values broken down by the categories of a selected dimension. They are also better equipped to show more categories at one time than a pie chart.